Downhole sources having enhanced IR emission

Light sources are provided with enhanced low-frequency (e.g., near infrared) emission. Some disclosed embodiments include a filament and at least one re-radiator element. The filament heats the re-radiator element to a steady-state temperature that is at least one quarter of the filament's absolute temperature. As disclosed herein, the increased surface area provided by the re-radiator element provides enhanced IR radiation from the light source. Patterning or texturing of the surface can further increase the re-radiator element's surface area. Various shapes such as disks, collars, tubes are illustrated and can be combined to customize the spectral emission profile of the light source. Some specific embodiments employ a coating on the bulb as the re-radiator element. The coating can be positioned to occlude light from the filament or to augment light from the filament, depending on the particular application. The various re-radiator elements can be positioned inside or outside the bulb.